In situ XRD study of C60 polymerisation above pressures of 9 GPa and temperatures up to 830K

The C60 polymerization was studied by X‐ray diffraction in situ in the pressure range 13–18 GPa and at temperatures up to 830 K. The results of the high pressure high temperature treatment are strongly dependent from the history of the sample and stress. At certain conditions no elliptical diffraction patterns were observed at 13 GPa and 830K. Samples with a relatively low internal stress showed a transformation to new phase. It is suggested that this phase is three‐dimensional polymer with each C60 molecule bonded to eight neighbors. This phase showed an increased hardness (about 37 GPa) and a Raman spectrum distinctly different from previously known polymeric phases.